1. Field of the Invention
This invention relates to telephone caller identification apparatus, and more specifically, to a calling identity delivery on call waiting apparatus using subscriber loop power during off-hook operation.
2. Description of the Related Art
Caller identification systems have been in use for a number of years. Operation of the caller identification apparatus requires detection of tones provided by the telephone service provider.
Call waiting service has also been provided by telephone service providers for a number of years. Alerting signals are provided by the service provider to alert the subscriber's equipment that another call is arriving while the telephone receiver is off-hook.
In order to provide caller identification service during off-hook operation, the caller identification apparatus must detect the Customer Premises Equipment Alerting Signal (CAS). This signal is provided by the Calling Identity on Call Waiting service (CIDCW).
Detectors for the CAS signal consume relatively large amounts of power, as the detection of the CAS tone is not as simple as detecting a ringing or hook reversal condition. The CAS detector must operate while the subscriber loop is in the off-hook condition and consumes power continuously while the user is connected to the service. Therefore, while caller identification apparatus in the present state of the art can be powered by a small battery, operation of caller identification in conjunction with call waiting services however requires more power. In response to the power requirement problem, caller identification apparatus designed for use with call waiting services are powered by a separate power supply connected to the subscriber's AC power service.
This is a cost disadvantage and is also an inconvenience to the subscriber. A power outlet may not be available near the desired location of the caller identification apparatus and a complete system requires an additional power supply and associated packaging, storage and shipping costs.
The present apparatus and method provide a solution to the problem by using the subscriber loop to power the CAS tone detectors while the telephone is off-hook.